超音波スペクトロスコピーによる加熱を受けたコンクリートの劣化度評価

Abstract

In this study, the ultrasonic spectroscopy was applied to evaluate quality of concrete exposed to high tempereture conditions, as one step to establish a new non-destructive testing technique for concrete and mortar. The main results obtained in this study are summarized as follows : 1) Compressive and flexural strengths of concrete decrease according to temperature rise, especially the flexural strength of mortar is sensitively affected by temperature rise. 2) Ultrasonic pulse velocity, maximum amplitude and energy of measured ultrasonic pulse wave decrease according to temperature rise, but energy moment and energy dispersion increase, independent of the water-cement ratio of test specimen. 3) Maximum amplitude and energy of frequency transfer function of concrete decrease with increase of temperature, and these decreasing rate is hardly affected by water-cement ratio and heating duration. 4) Local maximum amplitude and energy of the frequency transfer function in frequency ranges of 50-100kHz and 200-250kHz are closely related to change of internal structure of concrete exposed to high temperature.